Effects of the Total Alkaloidal Extract of Murraya koenigii Leaf on Oxidative Stress and Cholinergic Transmission in Aged Mice Vasudevan Mani, 1 * Kalavathy Ramasamy, 2 Aliya Ahmad, 1 Siti Norshazwani Wahab, 1 Siti Murnirah Jaafar, 1 Teh Lay Kek, 3 Mohd Zaki Salleh 3 and Abu Bakar Abdul Majeed 1 1 Brain Research Laboratory, Faculty of Pharmacy, Campus Puncak Alam, Universiti Teknologi MARA (UiTM), 42300, Bandar Puncak Alam, Selangor, Malaysia 2 Collaborative Drug Discovery Research Group, Faculty of Pharmacy, Campus Puncak Alam, Universiti Teknologi MARA (UiTM), 42300, Bandar Puncak Alam, Selangor, Malaysia 3 Pharmacogenomics Center, Faculty of Pharmacy, Campus Puncak Alam, Universiti Teknologi MARA (UiTM), 42300, Bandar Puncak Alam, Selangor, Malaysia Alzheimer’s disease (AD) is characterized by signs of major oxidative stress and the loss of cholinergic cells. The present study was designed to investigate the role of the total alkaloidal extract from Murraya koenigii (MKA) leaves on age related oxidative stress and the cholinergic pathway in aged mice. Ascorbic acid (100 mg/kg, p.o.) was used as a standard drug. The MKA improved the level of protective antioxidants such as glutathione peroxidase (GPx), reduced glutathione (GSH), glutathione reductase (GRD), superoxide dismutase (SOD) and catalase (CAT) in brain homogenate at higher doses (20 and 40mg/kg, p.o.). Moreover, a dose dependent decline was noted in lipid peroxidation (LPO) and the nitric oxide assay (NO) at all doses of MKA (10, 20 and 40 mg/kg, p.o.). Interestingly, significant progress was noted with the supplementation of MKA by an improvement of the acetylcholine (ACh) levels and a reduction in the acetylcholinesterase (AChE) activity in aged mouse brain. In addition, a significant elevation of serum albumin (ALBU), alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate transaminase (AST) and total protein as well as a decline in creatinine, total cholesterol, urea nitrogen and glucose levels with MKA also ameliorated the hepatic and renal functions in normal ageing process. The results showed the possible utility of Murraya koenigii leaves in neuroprotection against neurodegenerative disorders such as Alzheimer’s disease. Copyright © 2012 John Wiley & Sons, Ltd. Keywords: Murraya koenigii; ageing; oxidative stress; acetylcholine; Alzheimer’s disease. INTRODUCTION Oxidative stress due to an increase of free radical gener- ation or impaired endogenous antioxidant mechanism, is an important factor that has been implicated in cognitive deficits and Alzheimer’s disease (AD) in the elderly (Zhao and Zhao, 2012). It is well established that free radicals are associated with a process that leads to cell de- generation, especially in the brain (Shulman et al., 2004). However, the consumption of foods rich in antioxidant phytochemicals may help to fight degenerative diseases caused by oxidative stress through an improvement of the body’s antioxidant status. Furthermore, the most prominent neurochemical change in Alzheimer’s brain is a reduced concentration of acetylcholine in the hippocam- pus and neocortex, caused by degeneration of cholinergic neurons (Schliebs and Arendt, 2011). Cholinergic deficit is a major neuropathological feature that is associated with memory loss, and is closely correlated with the sever- ity of cognitive dysfunction in AD (Hasselmo, 2006). On other hand, cholinergic transmission is terminated mainly by ACh hydrolysis through the enzyme AChE, which is responsible for degradation of ACh to acetate and choline in the synaptic cleft (Ballard et al., 2005). Inhibition of AChE serves as a strategy for the treatment of AD. The drugs approved for AD therapy act by counteracting the acetylcholine deficit, that is, they try to enhance the acetylcholine level in the brain (Heinrich and Teoh, 2004). Murraya koenigii (Linn.) Spreng (Family: Rutaceae), commonly known as ‘curry leaves’, is popular as a spice and condiment among the Asians. The fresh leaves and its dried powder are traditionally added to gravy and other vegetables for the distinctive flavor and aroma. The leaves exhibit hypoglycemic and antidiabetic (Krishna and Usha, 2009; Tembhurne and Sakarkar, 2010), hepatopro- tective (Sathaye et al., 2011), antibacterial (Ningappa et al., 2010), wound healing (Gupta et al., 2009), chemomodu- latory (Dasgupta et al., 2003), immunomodulatory (Shah et al., 2008), antidiarrheal (Mandal et al., 2010), nephro- protective (Yankuzoa et al., 2011), antiobesity and lipid lowering effects (Birari et al., 2010). Our previous study demonstrated the antiamnesic potential of pow- dered Murraya koenigii leaves with normal diet fed continuously for 30 days to mice (Vasudevan and Parle, 2009). Moreover, a carbazole alkaloid mahanimbine from Murraya koenigii leaves was found to inhibit acetylcholinesterase (AChE) activity in vitro (Kumar et al., 2010). Several carbazole alkaloids, namely mur- rayanine, mahanimbine, girinimbine, murrayacine, isomur- rayazoline, isomahanimbine, koenimbidine mahanine, * Correspondence to: Vasudevan Mani, Brain Research Laboratory, Faculty of Pharmacy, Universiti Teknologi MARA (UiTM), Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor, Malaysia. E-mail: vasudevan@puncakalam.uitm.edu.my PHYTOTHERAPY RESEARCH Phytother. Res. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.4676 Copyright © 2012 John Wiley & Sons, Ltd. Received 16 November 2011 Revised 30 January 2012 Accepted 30 January 2012